As the breadth of microchip fabrication technology has continued to expand, an emerging technology associated with miniscule gadgets known as microfluidic devices has taken shape. Microfluidic devices, often comprising miniaturized versions of reservoirs, pumps, valves, filters, mixers, reaction chambers, and a network of capillaries interconnecting the microscale components, are being developed to serve in a variety of deployment scenarios. For example, microfluidic devices may be designed to perform multiple reaction and analysis techniques in one micro-instrument by providing a capability to perform hundreds of operations (e.g. mixing, heating, separating) without manual intervention. In some cases, microfluidic devices may function as detectors for airborne toxins, rapid DNA analyzers for crime-scene investigators, and/or new pharmaceutical testers to expedite drug development.
While the applications of such microfluidic devices may be virtually boundless, the integration of some microscale components into microfluidic systems has been technically difficult, thereby limiting the range of functions that may be accomplished by a single device or combination of devices. In particular, current microfluidic systems have not adequately integrated a size-separating (or excluding) filter into a microfluidic chip. As such, separations may generally be carried out in external packed porous media or polymer-based nanopore membranes, thereby increasing contamination risks and introducing additional complexity and manual interaction into the performance of an analysis or other technique.